1. Field of the Invention
The present invention relates to removable memory devices. In particular, the present invention relates to a removable memory device for a portable terminal device that can be removably connected to such a portable terminal device as, e.g., a portable telephone and can store therein ID information, a telephone number list, and so on, etc., inherent in each portable terminal device.
2. Description of the Related Art
Such a portable terminal device as a portable telephone comprises a memory device which stores therein, for example, such a telephone number list as abbreviated dialing numbers or such individual information as ID information inherent in each portable terminal device, entered by a user. When a user wants to exchange the portable terminal device with another due to user's upgrading to a newer device, it is desirable to enable copying of the individual information already stored in the portable terminal device used so far to a new portable terminal device and also to enable use of the new portable terminal device with the same individual information.
Disclosed in Japanese Patent Application Laid-Open Publication No. Hei-4-302245 is a system wherein an information memory device for storing information necessary for operation of a radio telephone set, i.e., operation lock/unlock information, radio telephone participation information, or attached function restriction information, private information (i.e., individual information) such as a telephone number list, as explained in Japanese Patent Application Laid-Open Publication No. Hei-4-302245, is made in the form of an ID card or a chip and the information memory device is arranged to be removably connected to the radio telephone device.
In that system, when it is desired to exchange the radio telephone device with a newer device, by just removing the information memory device from the old radio telephone device and then attaching it to the new radio telephone device, the user can use the new radio telephone device under the same environment (that is, the same individual information) as that of the old radio telephone device.
However, the prior art radio telephone device has a problem that, since anyone can simply remove the information memory device therefrom, when another user removes the information memory device from other's radio telephone device and attaches the information memory device to his or her own radio telephone device, he or she can use it with use of the other's individual information.